Those who know the diminutive Sir Nicholas Stern, Treasury and World Bank economist and author of today's groundbreaking report on the economics of climate change, know he is not necessarily the most political of economists.

Indeed, those who have worked with him have seen him tasked with simplifying British tax policy only for him to propose that VAT should be set at one level, including a massive rise in currently zero-rated VAT items.

Asked by a more senior figure in the Treasury whether these proposals amounted to good politics, Sir Nicholas has been known to reply that his job is not to answer the political questions, but simply provide the economics answers.

In the case of his review into the economics of climate change, Sir Nicholas has been equally fearless, but at least found himself operating in a surprisingly auspicious domestic political atmosphere.

The party conference season saw the Liberal Democrats and the Conservatives battling with one another for the green vote, both promising to raise green taxes as a proportion of the tax take.

In the unusually memorable words of former Tory chancellor Lord Howe the aim now is tax as you burn, rather than tax as you earn.

It was therefore incredibly unfortunate that someone - and no one knows who - leaked a letter by the environment secretary, David Miliband, proposing a rise in green taxes as part of the pre-budget report due early next month.

Mr Miliband's letter was a typical departmental bid, and was clearly using the political pressure generated by the Tory and Liberal Democrats conferences to put the heat on the chancellor.

The leak led to some very disastrous headlines in the Tory press in which it was claimed that the punter was going to have pay higher net taxes simply to pay for the prime minister and Mr Brown to cast themselves as world saviours.

It was particularly galling for Number 10 to see the Sun and Sky News adopt this approach only weeks after Rupert Murdoch had committed himself personally to green economics.

The mini-episode just shows how no one should assume that the British political culture is genuinely far-sighted and selfless in outlook.

Green economics, like welfare in the US, has the potential to become the third rail of UK politics.

But once the current cosy consensus on the level the green taxes the electorate are willing to pay is tested, the united front quickly starts to flake.

It is ever more likely that one political party or another in search of votes will take off the hair shirt, leaving the more puritanical parties to suffer at the polling booth.

It is therefore wise, and typical of the chancellor, that he should propose that the difficult decisions on green taxes should be hived off to an independent body, and also leave such decisions to later.

Mr Brown is not one to make big political moves quickly, and instead meticulously prepares the ground.

The prime minister was also wise to suggest that the Stern review is not primarily about Britain. After all, the UK is responsible for only 2% of total carbon emissions. It is instead about trying to create an international mood.

If this report has a target audience, it is not the Sun or the Daily Mail, it is instead the US Senate, the Indian Congress party, the German G8 presidency next year and whoever makes decisions in China.

The UK can show a lead, and it can do better than it has in cutting carbon emissions, but the answers lie in a global trading system that puts a penal price on carbon.

If such a system can be agreed, and a price can be set for carbon that everyone respects, then it is possible to incentivise all kinds of other decisions by companies - including whether it is worthwhile for a firm to invest in carbon-saving technology.

But these decisions need to be made quickly. Stern makes it clear that unless the big decisions on carbon trading, including the allocations and issuing of permits, are made within a decade, it will be too late.

All this requires a form of international governance that the world has conspicuously failed to show so far on issues such as war and peace, or relieving poverty in Africa.

The Brown camp is aware of this, yet he also knows that the public will want him to deal with the local and the particular, even though his instincts and experience has led him to believe the true answers lie in the global.